Unaccusative verb

An unaccusative verb is like when a toy falls off a shelf and hits the ground, or when you slip and fall down. It means that something happened by accident or by itself, without anyone else doing it.

In grammar, an unaccusative verb is a verb that describes an action that doesn't have a direct object. That means, it doesn't happen to anything or anyone else, it just happens by itself.

For example, "the vase broke" is an unaccusative sentence because the vase didn't break anything else, it just broke by itself. In contrast, "she broke the vase" is an accusative sentence because the subject (she) caused the action (breaking) to happen to the direct object (the vase).

Unaccusative verbs often describe things that are happening to the subject, like "She fell asleep" or "The building collapsed". These actions happen to the subject (her or the building) without anyone else causing them to happen.

So, when you hear or see an unaccusative verb in a sentence, it means that something is happening by itself or accidentally, without anyone else causing it to happen.